In magnetic resonance imaging, a large magnetic field is used to align the nuclear spins of atoms as part of the procedure for producing images within the body of a subject. Magnetic resonance imaging is typically used to map the location of protons, such as those in a water molecule, within a subject. Magnetic resonance imaging is much better than X-ray techniques such as CT at imaging soft tissues and showing the detailed anatomical structures of soft tissues. However, the large magnetic field and radio-frequency signals used for magnetic resonance imaging prevents the use of some materials, such as conductors, and electronics within the magnetic resonance imaging volume. This is because the radio-frequency electromagnetic field generated during magnetic resonance imaging may cause heating these materials or electronics and the surrounding tissues.
Eryaman et al, Magnetic Resonance in Medicine, Volume 65 (2011), pages 1305 to 1313, discloses the modification of the electric-field distribution of a radio-frequency coil to generate electric field-free zones in a subject without altering the transmit sensitivity.